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Topological Defects in Confined Nematics by Planar Anchoring

Seyed Nejad, Reza | 2012

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 43782 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Ejtehadi, Mohammad Reza; Mozaffari, Mohammad Reza
  7. Abstract:
  8. Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related equilibrium defect textures when the shell has isotropic and anisotropic shapes.
    Our calculations show that in the symmetric shells, the boojums defects(bipolar) appear in the thick shells and the tetrahedral defect arrangements (baseball) take place in the thin shells.In bipolar regimes while the shell has asymmetric geometry, the boojums defects transform to triangle configurations that their related energies in term of the center-center sphere displacements are included a minimum in each thickness of the shell. Our calculations in thinner regimes of the shell also show that the baseball configurations appear only in the symmetric shells so that in asymmetric configurations the baseball configurations transform to zonal shapes. The small negative and positive slops of the final energies in the zonal and the baseball defect arrangements respectively indicate that both configurations have a coexistence in closed of the symmetric geometry
  9. Keywords:
  10. Anchoring ; Nematic Droplet ; Degenerate Plannar ; Landau De-Gennes Energy ; Topological Defect

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